Electron discharge device



April 7, 1936. E. w HEROLD 2,036,696

ELECTRON DI SCHARGE DEVICE Filed Nov. 28, 1934 INVENTOR EDWARD W. HEROLD I? ATTORNEY Patented Apr. 7, 1936 UNITED STATES PATENT ()FFICE ELECTRON DISCHARGE DEVICE Delaware Application November 28, 1934, Serial No. 755,079

8 Claims.

My invention relates to electron discharge devices for superheterodyne reception and more particularh to a multi-electrode electron discharge device ,in which localoscillations of a predetermined frequency and input oscillations of a different frequencygsuch as a radio signal, are mixed or combined directly in the tube.

In radio receivers employing the superhetero- V dyne method of reception two different frequencies must be combined; that is, the frequency 01. the signal received by the antenna and usually amplified in the preceding stage must be combined with the local frequency produced by a local oscillator in, the receiver proper so that the heterodyne action will produce an intermediate frequency modulated in the samemanner as the signal frequency. w n

Usual. methods of heterodyne reception employ a first detector or mixer tube, in which the radio signal (input) frequency and the local frequency enerated in an oscillator circuit usually by a separate tube are both applied to the same grid of the mixer tube. These methods generally depend on coupling the oscillator and input circuits by either capacitive or inductive coupling which requires rather critical adjustment, and due to this coupling, changes in the signal input circuit affect the. operation of the oscillator and hence the local frequency.

Electron discharge tubes with high gain and in which heterodyne action may be obtained without undesirable intercoupling between the input (signal) and oscillator circuits have been proposed in which the oscillator grid and plate electrodes. are positioned in the stream of electrons which flows from the thermionic cathode to the signal or modulator grid and output plate. In this type of tube where the oscillator anode is in 40 the same electron stream as the modulator electrodes, undesired intercoupling between the oscillator and modulator sections is apt to be present. Furthermore any constructional changes in the oscillator section of the tube will have 45 a direct effect upon the operation of the signal responsive or modulator section of the tube, for example a-change in the turns per inch of the oscillator control grid wire will causea substantial change in the current of the output plate, 50; and for these reasons-it is diflicult to design the modulator (signal) and oscillator sections of the tube independent of each other and to screen them from each other in a manner to give the optimum operation for each. It has also been 55 found that with this type of electrode construction, particularly with a V-shaped filament as the cathode, a reduction in the conventional size of the electrode mount, which for certain types of small tubes is desirable, introduced design diniculties which were not easily overcome by well- 5 known mechanical expedients.

One object of the present invention is to provide an improved'electron discharge device with high gain and in which heterodyne action may be obtained without undesired intercoupling between the input and oscillator circuits.

Another object is to provide an electron discharge device of the oscillator-modulator type in which the operation of the oscillator section of the device is entirely independent of the modulator section of the device and to provide such a device readily adapted to be made in small sizes.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a perspective view with parts broken away of an electron discharge device embodying my invention; Figure 2 is a top end view with the top mica spacer removed of the electrode mount assembly shown in Figure 1, and Figure 3 is a circuit diagram of a representative type of circuit for operation of the device shown in Figures 1 and 2.

In the preferred embodiment of my invention the electron discharge device is provided with an evacuated envelope l0, having a cap H, and the usual stem and press I2, upon which the electrode assembly is mounted and electrically connected to a plurality of the usual lead-in wires and supports l3.

The electrode assembly is mounted between a pair of insulating discs l4 and 15, preferably of mica. The outer cylindrical electrode I6 is the main or output anode. A cylindrical suppressor grid I! may, if desired, be mounted within and concentric with the output anode. A cathode I8, which is shown 01' the filamentary type, but may be of the indirectly heated type is positioned within the anode H5. The filamentary cathode may conveniently be supported at its upper end by a spring I9 secured to support rod 2!].

In accordance with my invention there is positioned around the cathode I 8, a grid 2|, preferably in the form of a flattened helix suitably supported on side rods. Adjacent the oscillator grid 2| and on one side of the cathode is an oscillator anode 22, preferably a sheet of metal parallel to the plane of the cathode. The cathode, l8, grid 2| and anode 22 comprise the oscillator portion of the tube for generating local oscillations within the tube.

Mounted on the opposite side of the cathode from the oscillator anode is a signal or modu lator grid 23 preferably connected to cap I and surrounded by a flattened helical grid 24 which acts both as an accelerating grid for the electron stream and also as an electrostatic screen for reducing the direct capacity between the signal grid 23 and the other tube elements. These two grids are interposed between the cathode and the output anode I6 of the signal responsive ormodulator section of the tube.

In accordance with my invention, the electron discharge from the cathode I8 is divided into two electron streams leaving the cathode, and preferably flowing in opposite directions. One of the streams flows thru the oscillator grid 2| to the oscillator anode 22 and the other thru the modulator grids, comprising grids 2| and 23, to, the output anode. The grid 2| surrounding the cathode l8, altho mechanically constructed as a single grid, in effect is a pair of electrically connected grids, which could be separate mechanical structures, the grid lying between one side of the cathode and oscillator anode serving as an oscillator grid, and the other grid lying between the other side of the cathode and the output anode serving as a modulator grid, the electrical connection between the two grids serving to impress the oscillator frequency on the modulator grid. The oscillator frequency on the grid 2| modulates the electron stream leaving the cathode to the output anode so that the frequency of the local oscillator is imposed upon the electron stream passing thru the control or I signal grid 23, which further modulates the electron stream in accordance with the received radio signal frequency applied to the signal grid.

As a result of the above construction of an I electron discharge device made in accordance q the oscillator electrodes.

' with applicants invention the modulator or signal grid 23 is practically unafiected by voltage variations on the oscillator electrodes, so that there is no inter-action between this grid and The design of the tube is made more flexible inasmuch as the control grid of the oscillator and the signal grid 01' the modulator section maybe designed independently of each other for optimum performance. Applicants construction also reduces the number 7 of grids necessary, inasmuch as the. oscillator control grid 2| and the screen grid :24 take the place of three separate grids usually necessary in a tube in which all the electrodes are in one electronstream. This design also permits the filament type cathode to have a greater spread and hence a higher emitter efficiency. There is considerable saving in space over the conventional type of construction and the mounting is considerably simplified, reducing the possibilities for low resistance leakage paths and shorts in the.

comprising the condenser 35 and inductance 36 coupled to the next succeeding stage by means of inductance 31.

While I have indicated the preferred embodiments of myinvention of which I am now aware and have also indicated only one specific application forwhich my invention may be employed, it will be apparent that my invention is by no 'means limited'to the exact forms illustrated or .the use indicated, but that many variations may be made in the particular structure used and the purpose for'which it is employed without 'departing from the scope of my invention as set forth in the appendedclaims. 7

i What I claim as new is-- a 1. An electron discharge device having a ther-- mionic cathode and a grid electrode surrounding said cathode, a plurality of grids'and an anode positioned on one side of said cathode for providing a main discharge path between said cathode and said anode, and an auxiliary anode placed on the opposite side of said cathode from said plurality of grids and said main anode to provide a second discharge path between said cathode and said auxiliary anode.

2. An electron discharge tube having a thermionic cathode, a grid electrode surrounding said cathode, a main anode positioned on one side of said cathode, a control electrode between said main anode and said cathode, and a grid electrode surrounding said control electrode and permitting the passage of current between said cathode and said main anode, and an auxiliary anode placed on the opposite side of said cathode from said main anode to provide a discharge path between said cathode and said auxiliary anode.

3. An electron discharge. device having a ther-.

mionic cathode, an'oscillator anode and an output anode positioned on diiferent sides of said cathode to produce two separate and distinct electron streams from the cathode, an oscillator gridinterposed between said cathode and said oscillator anode and a control grid and a second grid positioned between said output anode and said cathode, said second grid being electrically connected to said oscillator grid and a screen interposed between said control grid and said second grid.

4. An electron discharge device having a thermionic. cathode, an oscillator anode and an out.-

put. anode positioned on different sides of said cathode to produce two separate and distinct electron streams from the cathode, an oscillator grid interposed between said cathode and said oscillator anode, a control grid adjacent said output anode, a second grid adjacent the cathode and between said cathode and said output anode and connected to the oscillator grid and a screen grid interposed between said control grid and said second grid.

' 5. An electron discharge device having a thermionic cathode, a grid surrounding said cathode, and an anode on one side of said cathode provid ing an oscillator portion for said electron discharge device, a signal grid on the opposite side of said cathode from said anode, a screen grid surrounding said signal grid, and a main anode surrounding the cathode, grids and said first anode.

6. An electron discharge device having a thermionic cathode, a grid surrounding said cathode, an anode on one side of said cathode providing an oscillator portion for said electron discharge device, a signal grid on the opposite side of said cathode from said anode, a screen grid surrounding said signal grid, a suppressor grid surrounding the cathode, grids and said first anode, and an output anode positioned around said suppressor grid.

7. An electron discharge device having a thermionic cathode, a grid electrode surrounding said cathode, an output anode positioned on one side of said cathode, a control electrode between said output anode and said cathode and a box-shaped electrode surrounding said control electrode and an oscillator anode placed on the opposite side of said cathode from said output anode and a suppressor grid placed between said output anode and the other electrodes in said discharge device and surrounding all the other electrodes in said tube.

8. An electron discharge device having a thermionic cathode, a grid electrode surrounding said thermionic cathode, an output anode positioned on one side of said thermionic cathode, a control electrode positioned between said cathode and said output anode, a screen electrode surrounding said control electrode, an oscillator anode positioned on the other side of said cathode from said output anode whereby oppositely extending discharge paths are provided between said cathode and anodes and a suppressor grid positioned between said output anode and the other electrodes in the tube and surrounding all of the other electrodes within said tube.

EDWARD W. I-IEROLD. 

